The invention relates to burner assemblies and, more particularly, to burner assemblies used in lamps, decorative lighting devices, and the like and having a plastic fuel container.
Burner assemblies for lamps, decorative lighting device and the like typically include a canister containing a liquid fuel and a cap for holding a wick and covering the canister. For disposable burner assemblies, the cap typically is stamped from a metal and the canister typically is molded from a plastic material and has a raised neck defining an opening through which the liquid fuel is introduced into the canister.
In one type burner assembly, the cap has a raised, central portion for holding a wick, an annular recessed portion surrounding the central portion and peripheral collar which fits over the rim of the opening in the canister. A generally vertical, annular wall interconnecting the collar and the recessed portion fits inside the canister neck. This annular wall is dimensioned so that it pushes against the inner wall of the canister neck and forms a positive seal therewith. A burner assembly employing such a mounting scheme is illustrated in FIG. 2 of U.S. Giangiulio Pat. No. 4,025,290.
Under some circumstances, such as when the canister is not properly vented, the capillary action of the wick continues after the flame has been extinguished, causing the liquid fuel to collect in the recessed area. Also, the liquid fuel can collect in the recessed area when the canister is squeezed or jostled, causing the liquid fuel to leak out through vent hole(s) in the cap.
In another type of burner assembly, the cap has a raised central portion and an intermediate portion interconnecting the peripheral collar and the central portion. The intermediate portion has a frusto-conical shape, i.e., tapers downwardly away from the raised central portion, so that there is no recessed area where the liquid fuel can collect. The peripheral collar fits over a outwardly extending lip on the rim of the canister opening and is crimped against the rim to form a seal and lock the cap in place on the canister. A burner assembly employing this mounting scheme is illustrated in FIG. 3 of U.S. Tendick Pat. No. 4,892,711.
The metal cap of such a construction can transfer heat from a burning wick to the plastic material in the region of the rim on the canister neck. The plastic material softens and the inward force exerted by the crimped collar can displace the upper portion of the neck inwardly enough to break the seal with the collar. When this occurs, the liquid fuel can leak past the collar any time the canister is tipped over or jostled.
Another type of mounting scheme is disclosed in U.S. Olsen Pat. No. 4,728,286.